Vacuum casting furnace

ABSTRACT

This disclosure relates to vacuum furnaces for pouring molds and includes a furnace apparatus having an interior capable of being evacuated and readily divided into a loading chamber and a pouring chamber with trackway means for transporting a mold first into the load chamber and then into the pouring chamber. Both chambers have access doors at opposite ends of the furnace and one of these doors provides access into the chambers to a platform which rides on the trackway. The furnace includes a further vacuum-holding chamber for housing the divider door so that it can be opened without breaking a vacuum on the other furnace chambers.

United States atent l-lulit et al.

[ 1 VACUUM CASTING FURNACE [72] Inventors: Gerald W. Hulit, Ridgewood; Frederick A. Greenburg, Denville; Edward Pirkey, Dover; Stanley C. Tingquist, Sparta, all of NJ.

[73] Assignee: Howmet Corporation [22] Filed: June 18, 1969 [21] App1.No.: 834,416

[52] U.S. Cl ..164/258, 164/335, 266/34 V [51] Int. Cl. ..B22d 27/16 [58] Field of Search ..164/258, 253, 335, 256, 257, 164/336, 337, 254; 266/34 V [56] References Cited UNITED STATES PATENTS 3,014,255 12/1961 Bussard et a1 ..164/258 X 3,235,243 2/1966 Taylor ..266/34 V 3,565,156 2/1971 Vollmer et al ..164/256 3,116,999 1/1964 Armbruster ..266/34 V 3,554,268 1/1971 Taylor et al ..266/34 V 3,520,657 7/1970 Frumerman ..266/34 UX 2,893,860 7/1959 Lorenz ..266/34 V 3,337,201 8/1967 Snyder ..266/34 V [4 1 Aug. 29, 1972 FOREIGN PATENTS OR APPLICATIONS 1,205,918 8/1959 France ..266/34 V 349,033 11/1960 Switzerland ..266/34 V 1,041,652 10/1958 Germany ..266/34 V Primary ExaminerJ. Spencer Overholser Assistant ExaminerV. K. Rising Att0rney-Pennie, Edmonds, Morton, Taylor & Adams 1 1 ABSTRACT This disclosure relates to vacuum furnaces for pouring molds and includes a furnace apparatus having an interior capable of being evacuated and readily divided into a loading chamber and a pouring chamber with trackway means for transporting a mold first into the load chamber and then into the pouring chamber. Both chambers have access doors at opposite ends of the furnace and one of these doors provides access into the chambers to a platform which rides on the trackway. The furnace includes a further vacuumholding chamber for housing the divider door so that it can be opened without breaking a vacuum on the other furnace chambers.

2 Claims, 7 Drawing lfi'gures PATENTEDwsze 1972 3.687.191

SHEET 1 OF 6 INVENTORS GERALD W. HU LIT FREDERICK A. GREE NBERG EDWARD PIRKEY STANLEY C.T|NGQUIST AT TOR N EYS FIG.

SHEET 2 UF 6 INVENTORS GERALD W. HULIT FREDERICK A. GREENBERG EDWARD PIRKEY STANLEY C. TINGQUIST ATTORNEYS P'ATENiimuszs I972 PAIENIEnwm I912 3.687.191

SHEET 3 OF 6 l \tv 10 PAIENTEDwm m2 3.687.191

SHEEI h UF 6 INVENTORS GERALD W. HULlT FREDERICK A.GREENBERG EDWARD PIRKEY STANLEY C. TINGQUIST AT TO RN EYS BACKGROUND OF THE INVENTION Metals and metal compounds are processed under a vacuum to avoid oxidation and to provide a condition which promotes deoxidization with carbon in the metallic melt and to remove dissolved gases, such as hydrogen and nitrogen. The melting and pouring of molds to form castings is carried out under a vacuum to accomplish these objectives and in addition, the molds may be held in an evacuated chamber prior to pouring to remove entrained air and after pouring to prevent oxidation of the cooling casting.

Various devices have been proposed to accomplish the pouring of molds in an evacuated chamber and some have been directed to handling and pouring of the molds but none have provided a compact multichamber arrangement of the present invention which permits all production steps including handling, charging, pouring and cooling, to be readily carried out on large sized molds.

SUMMARY OF THE INVENTION The present invention provides an apparatus for handling molds of varying sizes including means for transporting the molds and the charges into the evacuated chambers of the furnace and means for readily closing, sealing and evacuating the various chambers to accomplish the required steps to produce good quality castings in a rapid sequence.

Broadly, the present invention comprises an apparatus for melting a metal charge and pouring the charge into a mold in an evacuated space comprising a walled enclosure, means for evacuating the enclosure, retractable closure means for dividing the enclosure into a loading chamber and a pouring chamber and a divider means chamber communicating with the enclosure for accommodating the divider means to permit a vacuum to be held on the other chambers when the divider means is retracted. Trackway means are provided for moving molds into and out of the chambers through an access opening which also has retractable closure means.

A further feature of the invention is that the furnace chamber may include a crucible for receiving, melting and casting the metal charges which crucible is mounted to be pivotable toward the pouring chamber access door to facilitate inspection, cleaning and charging of the crucible.

It is also a feature of the invention that a charging chamber is associated with the pouring chamber to permit charging of the crucible without breaking vacuum on the pouring chamber. The apparatus also includes means for removing a cover on the mold after the mold has been placed in the apparatus enclosure and the enclosure has been evacuated.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawing; FIG. 1 is a side elevation view of the furnace; FIG. 2 is a sectional view taken along line 2-2 of FIG.

F IG. 3 is a front elevational view; FIG. 4 is a plan view of the furnace and evacuating system with a partial section showing the trackway and conveying means;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a sectional view taken along line 66 of FIG. 4; and

FIG. 7 is an enlarged partial side elevational view showing the charging means and mold cover remover;

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I, vacuum furnace 1 has an interior enclosure which includes a rectangular shaped load chamber 3, a pouring or furnace chamber 5 and an elongated divider door chamber 6 (FIG. 3) extending from the side of the furnace. Load chamber 3 has a rectangular opening 4 which has substantially the same height and width as the chamber and pouring chamber 5 similarly has an opening 8 at the opposite end of the furnace which opening generally corresponds to the vertical cross-section of the chamber. A mold conveyor system 7 conveys the mold into and out of the furnace. Load chamber door 9, pouring chamber door 11 and center divider or partition door 13 are supported on overhead carriages 15 and all chambers and doors are reinforced with steel beams 17 to permit a high vacuum to be taken on each chamber.

Pouring chamber 5 has a charging chamber 19 to permit a charge of metal to be lowered into pivotable pouring crucible unit 21 without breaking vacuum on the pouring chamber (FIG. 4). Crucible unit 21 is heated by induction coils to melt the charge placed in it.

Referring to FIG. 1, 2 and 7, charging chamber 19 is positioned on the horizontal top wall 29 of chamber 5. Wall 29 has opening 31 (FIG. 2) which is closed by pivotable plate closure member 33. Door 32 provides access to the chamber to place the metal charge 37 on top of plate 33. Hydraulically-operated charge lowering device 34 includes hydraulic cylinder 36, verticallydisposed piston rod unit 38 and tong grippers 40. Hydraulic supply lines 42 provide hydraulic fluid to lower and raise the grippers 40. Grippers 40 are readily engageable with the indents 30 in charge 37. After evacuating chamber 19 through line 41 which is connected to the evacuating system, plate 33 is opened by turning axle 35 by an suitable air-tight means until the member is positioned as shown in dashed lines in FIG. 2. As plate 33 is moved stationary retaining arm 39 or tong grippers 40 hold charge 37 against lateral movement permitting the plate to slide out from under charge 37 so that the charge may be lowered through opening 31 into crucible 21. Tongs 40 release when the charge is supported by the crucible.

Referring to FIGS. 1, 3 and 4, the mold conveying system 7 includes a plurality of rollers 43 journaled near their ends in two rows of bearings 45 secured on parallel spaced apart longitudinal supports 47 to form trackway 48. Rollers 43 have pairs of flanges 44 secured to their central portions and spaced apart a sufficient distance to accommodate a guide runner 49 which is secured to the underside of a mold carrying pladorm 51. Outer platform runners 53 provide together with guide runner 49 three surfaces which move over rollers 49 of trackway 48 when the rollers are rotated by drive unit 55. Mold 56 is positioned on platform 51 in a position so that when crucible 21 is poured it will pour into the mold. The mold may be placed on a stand on the platform to position the mold a distance above the platform thus reducing the distance the molten metal is poured. Mold 56 has a pivotable cover 58 to prevent dust and dirt from entering the mold prior to its being poured. Cover 58 is connected to a suitable line and pulley system 60 so that the cover 58 is not opened during its movement through the chamber while being readily pivoted open by operation of handles 64 when the mold is ready for pouring.

Drive unit 55 includes three drive rollers 57 positioned among the rollers of trackway 48 at spaced intervals with each drive roller and each driven. roller 43 having a sprocket secured to it so that each drive roller 57 drives a group of rollers 43 through a chain 59. The three drive rollers 57 have sprockets 61 secured to their ends and are driven through chain 63 by hydraulic motor 65. Idler rollers 62 guide and tension belt 61 (FIG. 1).

In FIGS. 1, 3 and 6, overhead carriages l ride on horizontal rails 77 and include pairs of flanged wheels 79, axles 81 and frame 83.

In FIGS. 3 and 4, the chambers are evacuated by three two-stage vacuum pumps 84 having first stage units 87 and second stage units 85. Pumps 84 take a suction on branch conduits 89 which are each connected to manifold conduit 91. Load chamber 3 has two evacuating conduit lines, one line 93 leads through air filter 95 and the other line 97 by-passes the filter. Valves 99 and 101 permit pumps 84 to evacuate load chamber 3 through either line 93 or 97. Since filter 95 impedes molecular flow at low pressure levels, more efficient pumping is attained when the filter is bypassed. During initial pumping out of the chamber the filter collects dirt and dust in the evacuated air to protect the pump mechanism. The furnace or pouring chamber 5 may be separately evacuated through lines 3 and diffusion pumps 105.

Turning to FIG. 6, partition door 13 is moved against opening 18 of furnace chamber 5 to maintain an air tight seal with the chamber. Units 107 which are mounted in wall 1118 of load chamber 3 include shoes 109, piston rods 111 and hydraulic cylinders 113. High pressure oil is introduced into cylinders 113 to urge piston rods 111 to the left to hold door 13 against pouring chamber 5. Preferably four units 107 are used to hold door 13 in the closed position. Door 13 will hang straight down on chain '73 when not seated against chamber 5 and is carried back into elongated chamber 6 by carriage when platform 51 is required to be moved in or out of the chamber 5. Chamber 6 is secured to an elongated opening in the furnace enclosure (FIG. 4). Chamber 6 communicates with chamber 3 and is evacuated therewith and chamber 6 is easily removable from chambers 3 and 5 to facilitate maintenance.

The use of retractable rolling doors which can be moved to one side of the furnace when fully opened together with the arrangement of the evacuating equipment between the retracted positions of the three doors provides a novel compact arrangement of chambers, doors and evacuating equipment.

The charge 37 is lowered into the melting crucible in chamber 5. Doors 13 and 8 are closed and clamped. Chamber 5 is then evacuated and power is applied to the crucible for melting the metal. When the metal charge is molten the casting mold is introduced into chamber 3 by means of platform 51 of the conveyor system 7. Door 9 is closed and chamber 3 is evacuated.

When the pressures in chambers 3 and 5 are approximately equal door 13 is opened. The mold is moved up to the crucible and as soon as the metal reaches proper pouring temperature it is poured into the mold. The mold may then be withdrawn from the furnace by moving the platform into the load chamber closing the divider door 13, opening the load chamber door and moving the platform outside the furnace. When the divider door is closed, holding units 107 are energized to hold the door closed. This procedure permits the vacuum on the pouring chamber to be retained.

The crucible 21 may be recharged without breaking vacuum on pouring chamber 5 by opening door 32 of charging chamber 19 and placing a charge on closure member 33 within the chamber. Door 32 is then closed, chamber 19 evacuated and closure member 33 pivoted to permit the charge to be placed in the crucible by lowering device 34. When charge 37 strikes crucible 21 tongs 49 open to release the charge. When lowering device 34 is retracted back into chamber 19, closure member 33 is moved to close opening 31 to prevent loss of vacuum in chamber 5 when chamber 19 is opened.

While a charge is melting, another mold can be loaded into the load chamber and the chamber evacuated to prepare that mold for pouring. Where the poured molds are required to be cooled in an evacuated area to avoid atmospheric contamination, the mold can be left in the load chamber after pouring for a desired period of time.

Pouring chamber door 11 may be opened from time to time for cleaning and inspection of the crucible which may be tilted toward the pouring chamber opening 8 to facilitate the cleaning and inspection. The crucible unit may also be charged through this door when convenient.

It is seen that the steps of loading, charging, pouring and cleaning may be varied to provide for the most efficient and speedy production arrangement depending on the availability of molds ready for casting, the type of casting to be produced and the length of time required for melting and cooling of the casting in an evacuated area. Rapid and complete evacuation of the selected chambers is accomplished by using more than one pump and 'by-passing the air filter after the chamber has been substantially evacuated.

We claim:

1. A vacuum casting apparatus for melting a metal charge and casting molten metal in an evacuated space comprising a a compact walled enclosure b an elongated opening in a central portion of an outer wall of the enclosure,

0 an elongated chamber connected to the elongated opening in the outer wall of the enclosure,

d divider door means slidably positioned in the elongated chamber and capable of movement through the elongated opening for dividing the enclosure to form a load chamber and a pouring chamber,

e crucible means pivotably positioned in the pouring chamber for receiving, melt-ing and casting a metal charge,

f an opening in the load chamber to permit the loading and unloading of the mold,

g an opening in the pouring chamber positioned substantially opposite the load chamber opening, the pouring chamber opening permitting access for cleaning and charging of the crucible means,

h a first vacuum-retaining closure means for closing the load chamber opening,

i a second vacuum-retaining closure means for independently closing the pouring chamber opening,

j evacuating means operably connected to the enclosure for evacuating each of the chambers,

k a trackway positioned within both the load and pouring chambers and extending a distance outside the load chamber to facilitate loading,

1 a platform adapted for reciprocal movement on the trackway to carry a mold through the load chamber opening into the chambers and to withdraw the cast mold from the chambers,

m power means for controllably moving the platform on the trackway,

n a mold cover pivotably mounted on the mold, and

o mold cover moving means attached to the mold cover and operatively connected to a control handle means on the enclosure to permit covering of the mold during its movement through the enclosure and removing of the cover just prior to pouring of the melt from the crucible.

2. The apparatus of claim 1 in which the mold moving means is a line and pulley system. 

1. A vacuum casting apparatus for melting a metal charge and casting molten metal in an evacuated space comprising a. a compact walled enclosure b. an elongated opening in a central portion of an outer wall of the enclosure, c. an elongated chamber connected to the elongated opening in the outer wall of the enclosure, d. divider door means slidably positioned in the elongated chamber and capable of movement through the elongated opening for dividing the enclosure to form a load chamber and a pouring chamber, e. crucible means pivotably positioned in the pouring chamber for receiving, melting and casting a metal charge, f. an opening in the load chamber to permit the loading and unloading of the mold, g. an opening in the pouring chamber positioned substantially opposite the load chamber opening, the pouring chamber opening permitting access for cleaning and charging of the crucible means, h. a first vacuum-retaining closure means for closing the load chamber opening, i. a second vacuum-retaining closure means for independently closing the pouring chamber opening, j. evacuating means operably connected to the enclosure for evacuating each of the chambers, k. a trackway positioned within both the load and pouring chambers and extending a distance outside the load chamber to facilitate loading, l. a platform adapted for reciprocal movement on the trackway to carry a mold through the load chamber opening into the chambers and to withdraw the cast mold from the chambers, m. power means for controllably moving the platform on the trackway, n. a mold cover pivotably mounted on the mold, and o. mold cover moving means attached to the mold cover and operatively connected to a control handle means on the enclosure to permit covering of the mold during its movement through the enclosure and removing of the cover just prior to pouring of the melt from the crucible.
 2. The apparatus of claim 1 in which the mold moving means is a line and pulley system. 